Interpretive Summary: Foot-and-Mouth Disease (FMD) is a highly infectious viral disease of livestock that has significant economic, social and environmental impacts. One problem hampering the diagnosis, control and eradication efforts during large outbreaks is the need for veterinarians to inspect hundreds of animals from suspected case premises. The development of pen-side screening tests to quickly identify potentially infected animals for confirmatory diagnostic testing has the potential to save not only the lives of animals but also time and effort of farmers, veterinarians, laboratory technicians, and government officials. In this study, we assessed infrared thermography (IRT) as a means of detecting foot-and-mouth disease virus (FMDV)-infected cattle before the development of clinical signs. Our results showed that IRT could identify FMD infected cattle before any other clinical sign was visible. This technology shows promise and could be applied in the control and eradication of FMD.

Technical Abstract:
Foot-and-mouth disease (FMD) is a highly infectious viral disease of livestock that has significant economic, social and environmental impacts. One problem hampering the diagnosis, control and eradication efforts is the need for veterinarians to inspect hundreds of animals from suspected case premises. The development of pen-side screening tests to quickly identify potentially infected animals for confirmatory diagnostic testing has the potential to save not only the lives of animals but also time and effort of farmers, veterinarians, laboratory technicians, and government officials. In this study, we assessed infrared thermography (IRT) as a means of detecting foot-and-mouth disease virus (FMDV)-infected cattle before the development of clinical signs. Preliminary IRT imaging demonstrated that foot temperatures increased in FMDV-infected animals. The maximum foot temperatures of healthy (n=53), directly inoculated (DI) (n=12), contact (CT) (n=6), and vaccine trial (VT) (n=21) cattle were measured over the course of FMD infection. A pre-clinical cut-off value was established at 34.4 deg C (sensitivity=61.1%, specificity=87.7%) with the aim of detecting FMDV-infected animals in herds. Seven of 12 (58%) DI and 3/6 (50%) CT animals showed maximum foot temperatures exceeding the 34.4 deg C cut-off before the development of foot vesicles. In contrast, only 5/21 (24%) VT animals displayed pre-clinical foot temperatures above this cut-off indicating partial vaccine protection of this group. Besides lesion development, we also show the relationship between “hot feet” and the onset of viremia and fever. These results show IRT as a promising screening technology for detection of FMDV-infected animals with potential application during FMDV outbreaks.